Recent data suggest that high doses of supplemental pancreatic enzymes increase the risk of fibrosing colonopathy in some children with CF. To reduce the risk of this complication and to maximize the effectiveness of enzyme therapy, clinicians will use adjuvant therapies (H2-antagonists or Omeprazole) in conjunction with supplemental enzymes to improve fat absorption. Steatorrhea persists in many patients despite concomitant therapy. The objective of this study was to compare the efficacy and tolerance of an enteric-coated, bicarbonate-buffered pancrelipase preparation, PANCRECARB, with standard therapy in a cohort of children with CF and steatorrhea. Study Design: Fifteen children with CF and pancreatic insufficiency on lipase doses greater than 2500 U/kg/meal were identified. Patients completed a 72-hour fecal fat collection at home using a 3-day weighed diet record. Seven patients with <86% coefficient of fat absorption (COA) were enrolled in the open labeled, 3-week study period. Patients discontinued H2-antagonists and Prilosec. Phase I (Days 1-6). During the first study week, patients consumed their prescribed enzyme preparation along with a strictly regulated diet for fat and calories. All food was pre-and post-weighed by the study coordinator. Following 3 days at home on the study diet, patients were admitted to the CRC on days 4-6 to complete a 72-hour fecal fat collection. Daily symptoms and enzyme consumption were recorded. Phase II (Days 7-20) - Subjects consumed PANCRECARB( at 2 the enzyme dose in Phase I or equivalent to 1800-2000 U/kg/meal. During days 15-20 of the study, patients consumed the same weighed and regulated study diet as in Phase I. A fecal fat test was performed in the hospital during days 18-20 under the same conditions in Phase I. Results: Five patients (mean age 14.6 " 3.0 years, 4 male, 1 female) have completed the study. Mean fat and caloric intakes of 92"30 g/day and 2781"925 kcal/day in Phase I of the study were not significantly different from mean fat and caloric intakes of 88"21 g/day and 2834"927 kcal/day in Phase II (p=NS). A mean absolute change in COA of -6% between the prescribed enzyme therapy, Creon, and PANCRECARB was not clinically significant (p=NS). Average reduction in lipase dose/kg/meal was approximately 42%. Patients experienced a range of symptoms while on PANCRECARB in Treatment Phase II. Conclusions: Treatment with buffered-pancrelipase therapy did not yield a marked increase in COA during the study period. However, patients maintained their COA off adjunctive therapy with acid blockers at reduced lipase doses. Therefore, buffered-pancrelipase may provide clinical advantages for patients.